Arthrodesis is an operation for fusing two or more bones together. Such an operation is performed to relieve pain caused by a fracture or arthritis. For example, many individuals suffer from wrist arthrosis, which may require fusion of the lunate, the capitate, the hamate, and the triquetrum bones.
One method of fusing these four bones together includes the step of milling out a part of each bone in order to implant a fusion plate. The fusion plate is configured to connect all four bones together by means of screws, so that the four bones can fuse together. During the milling step, however, the four bones have a tendency to elastically move apart from each other due to the force with which the milling reamer is pushed towards the bones. The separation of the bones during the milling may lead to an inaccurately milled countersink. When the fusion plate is to be positioned within the countersink, the diameter of the plate may be bigger than the countersink once the bones move elastically back towards each other.
Moreover, with the current methods, it may be difficult to find the proper location at which the bones are to be milled by the reamer. This is because the countersink is typically made free hand without the use of guides or other aids.